Lubricant



United States Patent 3,278,431 LUBRICANT Arnold J. Morway, Clark, and William E. Wellman, Edison, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Sept. 27, 1963, Ser. No. 312,009 5 Claims. (Cl. 25239) This invention relates to lubricants containing salts of phoronic acid or its homologues. Particularly, the invention relates to lubricating fluids and greases comprising lubricating oil containing metal salt of phoronic acid materials, i.e. phoronic acid or its homologues, and preferably containing metal salts of various fatty acids.

Metal salts of phoronic acid materials have been found useful as an additive for lubricating oil, and in making grease. These salts are useful as grease thickeners per se, and are particularly useful as structure stabilizers for a variety of greases thickened primarily with other salts or soaps. From the standpoint of stabilizing a grease structure, these salts of phoronic acid materials impart similar properties to greases as does 12-hydroxy stearate. Thus, one of the most effective agents for stabilizing many greases from softening by extended mechanical working is l2-hydroxy stearate. It is believed that the hydroxy groups of the l2-hydr-oxy stearate molecules may act as bonds which link together the various soap molecules to help give the grease structure. Upon shearing by mechanical working, it is believed that these bonds may reform upon the cessation of the shearing so that the structure, e.g. the penetration of the grease, changes little upon mechanical working. In a similar manner, it is speculated that the keto group of the phoronic acid materials of the invention may form bonds in a manner similar to 12-hydroxy stearate with essentially the same good results in stabilizing the grease and possibly, are more effective since the shorter chain lengths of the phoronic acid materials are less susceptible to shearing than 12-hydroxy stearate.

In addition, the salts of phoronic acid are superior to the corresponding salts of 12-hydroxy stearic acid for grease-making in that they have a higher metal content which appears in many cases to result in a considerably longer lubricating life at elevated temperatures. Furthermore, 12-hydroxy stearic acid is available only commercially from castor oil and is relatively expensive. On the other hand, phoronic acid generally imports structural stability as effectively as the IZ-hydroxy stearic acid and can be prepared from acetone, or from phorone, which is a by-product of a process for making methylisobutyl ketone.

The phoronic acid material of the invention has the following structure:

wherein n is 1 to 3. When both ns are 1, then the material is phoronic acid.

Phoronic acid is the preferred material of the in- Patented Oct. 11, 1966 vention and can be prepared from phorone according to the following process:

H 0 C H,

/ NaC N The preceding process has been described in Anschiitz, R., Berichte, 26, 827 (1893); Lapworth, J. Chem. Soc. Lond., 83, 9991003; and Rudolph, Technical Oil Mission, Reel 22, Frames 760000894-902.

The phorone used in the preceding process is a known chemical and its preparation has been described in detail in German Patent 483,823 to Leopold, R., and Schacke, B.

Metal salts, e.g. alkali metal or alkaline earth metal salts, of the phoronic acid material can be dispersed in lubricating oil to form useful lubricating fluids and greases in amounts of 0.1 to 40.0 wt. percent, e.g. 1.0 to 10.0 wt. percent, based on the total weight of the lubricant. However, the salts of phoronic acid are particularly useful as a component of mixed-salt systems. These mixed-salt systems can contain salt of 0.3 to 24.0 parts by weight of C to C fatty acid per part by weight of phoronic acid material. For example, the system can contain salt of 0.3 to 4.0, preferably 0.5 to 2.0, parts by weight of low molecular weight C to C fatty acid per part by weight of phoronic acid material. These systems can also contain salt of .1 to 20, preferably .5 to 10, parts by weight of intermediate and/or high molecular weight carboxylic acid per part of weight of phoronic acid material. Greases can be prepared containing about 10 to 40.0 wt. percent, e.g. 10 to 35 wt. percent, of the total mixed salt, i.e. total of fatty acid salt and phoronic acid salt. These greases in turn can be diluted with additional oil to form fluid or semi-fluid compositions containing about 0.1 to 10.0 wt. percent of the total mixed salt. The preceding weight percents are based on the total wei ht of the composition.

Suitable low molecular weight acids for forming mixed salt compositions include C to C saturated or unsaturated, substituted and unsubstituted, aliphatic monocarboxylic acids. These acids include fatty acids such as formic, acetic, propionic, and similar acids including their hydroxy derivatives such as lactic acid, etc. Acetic acid or its anhydride is preferred. Mixtures of these low molecular weight acids may be employed if desired.

Intermediate molecular weight carboxylic acids which may be used include those alpihatic, saturated or unsaturated, unsubstituted, monocarboxylic acids containing 7 to 12 carbon atoms per molecule, e.g. capric, caprylic, nonanoic, lauric acid, etc.

The high molecular weight carboxylic acid includes naturally-occurring or synthetic, substituted, or unsubstituted, saturated or unsaturated, mixed or unmixed fatty acids having about 13 to 30, e.g. 16 to 24 carbon atoms per molecule. Examples of such acids include myristic, palmitic, stearic, arachidic, oleic, ricinoleic, hydrogenated fish oil, tallow acids, etc.

The lubricating oil used in the compositions of the in vention may be either a mineral lubricating oil or a synthetic lubricating oil. Synthetic lubricating oils which may be used include esters of dibasic acids (e.g. di-Z-ethylhexyl sebacate), esters of glycols (e.g. C Oxo acid diester of tetraethylene glycol), complex esters (e.g. the complex ester formed by reacting one mole of sebacic acid with two moles of tetraethylene glycol and two moles of 2-ethyl-hexanoic acid), halocarbon oils, alkyl silicates, sulfite esters, mercaptals, formals, polyglycol type synthetic oils, etc., or mixtures of any of the above in any proportions. If the salts are formed in situ in the oil, then this in situ reaction is best carried out in a mineral oil, since some synthetic oils will tend to decompose or hydrolyze during the salt formation. However, the salts once formed, can be used in lubricants containing the synthetic oils noted above.

Various other additives may also be added to the lubricating composition in amounts of 0.1 to 10.0 weight percent each. Such additives include oxidation inhibitors such as phenyl-alpha-naphthylamine; corrosion inhibitors such as sorbitan monooleate, sodium nitrite; dyes; other grease thickeners; and the like.

The lubricants of the invention can be formed in a number of different ways. The most convenient Way is to neutralize the acid with metal base in oil. Usually, the resulting composition will then be heated to about 225 F. to 600 F., preferably 400 F. to 757 F. to dehydrate the composition. In general, particularly when using acetic acid or its anhydride, the higher temperature of 400 F. to 600 F. will result in the formation of a salt material having greater thickening effect and better load and e.p. properties than lower dehydration temperatures, e.g. 300 to 350 F.

The invention will be further understood by the following examples, which include preferred embodiments of the invention and wherein all parts are by weight.

EXAMPLE 1 A grease was prepared as follows:

15 parts of Hydrofol Acids 51, 71.9 parts of a solvent refined mineral lubricating oil of 60 SUS viscosity at 210 F. and 3 parts of phoronic acid were added to an electrically heated grease kettle and warmed while mixing to 125 F. Hydrofol Acid 51 is hydrogenated fish oil acid having a Saponification No. of about 200, an Iodine number of about and averaging about a C chain. 6.1 parts of lithium hydroxide monohydrate (LiOH-H O) in the form of a aqueous solution, i.e. 10 wt. percent lithium hydroxide monohydrate and 90 wt. percent water, was added to the kettle. The addition of the LiOH-H O was followed immediately by 3 parts of glacial acetic acid. Heating was then initiated and the temperature of the kettle contents raised to 440 F. and held at this temperature for about one-fourth hour in order to dehydrate the grease. The grease was then cooled to 250 F. where 1 part of phenyl-alpha-naphthylene was added as an oxidation inhibitor. The grease was further cooled to 110 F. The product was then homogenized by passage through a Morehouse mill having 0.003" clearance.

4 EXAMPLE 2 3 parts of the grease of Example 1 was intimately mixed at room temperature with 1 part of additional mincral lubricating oil of 60 SUS viscosity at 210 F.

Grease A A comparison grease was prepared in the same manner as that of Example 1 except that no phoronic acid was used.

Grease B CH CH3(CH))r--(CH2) CO2H wherein x+y=7, and x: 1, 2, or 3.

The compositions and the properties of the greases of Examples 1 to 2, and the Comparison Greases A and B, are summarized in the following table.

TABLE I Examples 1 Comparison Composition (wt. percent):

Hydrofol Acid 51 Glacial Acetic Acid. 3 Phorouic Acid a 3.

Lithium Hydroxide Me Oh drate (LiOH-HIO) Phenyl-Alpha-Naphthy amine Mineral Lubricating Oil, 60

SUS. at 210 F Gm Dicarboxylic Acid (Dibasic Branched Chain Acid) Properties:

Appearance Dropping Point, F ASTM Penetration, 77 F.,

Unworkcd Worked 60 Strokes. Worked 100,000 Strokes Water Solubility Lubrication Liiefl Hours:

10,000 r.p.m. 300 F 10,000 r.p.n1. 250 F 2, 0

1 Excellent.

2 Grainy.

4 Insoluble.

ABEC-NGLI Spindle Test.

As seen by the preceding table, the products of the invention are represented by Examples 1 and 2 which gave excellent smooth homogeneous appearing greases. In addition, these greases were exceptionally stable to mechanical working as illustrated by comparing their unworked penetrations with the penetrations after 100,000 strokes. On the other hand, Comparison grease A shows that without the phoronic acid material, a grainy grease resulted, which because of its poor appearance was not tested any further. Comparison B shows that use of a dicarboxylic acid per se, i.e. the C dicarboxylic acid, does not impart the stability of mechanical working obtained by using the phoronic acid. Thus, note that the grease of Comparison B became semi-fluid upon being worked 100,000 strokes. In addition, the g a P pared from phoronic acid had exceptionally long lubrication lives at elevated tempenatures as shown by the ABEC-NLGI spindle tests.

EXAMPLE 3 A grease was prepared which was thickened solely with the sodium salt of phoronic acid to demonstrate its ability to serve as the sole thickening agent. This grease was prepared as follows:

15 parts of phoronic acid and 78 parts of a mineral lubricating oil 55 SSU viscosity at 210 F. was added to a grease kettle and warmed to 120F. while intimately mixing. 6 parts of sodium hydroxide was then added to the kettle in the form of a 40% aqueous solution, i.e. 40 wt. per cent NaOH dissolved in 60 wt. percent water. The resulting mixture was then heated, evaporating water until a temperature of 350 F. was reached. At this point, the heat was turned off and the composition was cooled to 250 F. One part of phenyl-alpha-n aphthylamine was added, following which the composition was cooled at 120 F. The composition was then homogenized by passage through a Morehouse mill having a 0.003 inch clearance.

The formulation and the main physical properties of of the product of Example 3 described above are summarized in the following table.

As seen by the preceding table, phoronic acid may be used as a sole thickening agent. However, its preferred used use is in the formation of grease thickened primarily with other thickeners, egg. the water-insoluble greases of Examples 1 and 2 previously described.

What is claimed is:

1. A lubricating grease comprising a major amount of lubricating oil and about to 45 wt. percent of mixed metal salt of C to C fatty acid, C to C fatty acid and phoronic acid material of the formula:

wherein n is 1 to 3, wherein said metal is selected from the group consisting of alkali metals and alkaline earth metals, and wherein the proportion of said C to C fatty acid is about 0.3 to 4.0 parts by weight per part by weight of said phoronic acid material, and the proportion of said O, to C fatty acid is about 0.1 to 20 parts by weight per part by weight of said phoronic acid material.

2. A lubricating grease according to claim 1, wherein said phoronic acid material is phoronic acid, and said C to C acid is acetic acid.

3. A lubricating grease according to claim 2, wherein said metal is calcium, and the proportion of acetic acid to phoronic acid is .5 to 2.0 parts by weight of actic acid per part by weight of phoronic acid, and the proportion of Cq to C acid is .5 to 10 parts by weight per part by weight of phoronic acid.

4. A lubricant comprising a major amount of mineral lubricating oil, about 10 to 40.0 wt. percent of lithium salt of 0.3 to 4.0 parts acetic acid, 0.1 to 20 parts of C to C fatty acid, and one part phoronic acid, said salts being prepared by coneutralizing all of said acids in at least a portion of said oil with lithium base.

5. A lubricant according to claim 4, wherein about 0.5 to 10 parts of said C to C fatty acid per part of salt of phoronic acid is used, and wherein the total amount of said lithium salt is about 10 to wt. percent of the total lubricant.

References Cited by the Examiner UNITED STATES PATENTS 10/1952 Sproule et al. 252-39 3/1959 Morway et al 252-39 X 3/1961 Morway 25239 X FOREIGN PATENTS 1/1963 Canada.

DANIEL E. WYMAN, Primary Examiner,

I. VAUGHN, Assistant Examiner. 

1. A LUBRICATING GREASE COMPRISING A MAJOR AMOUNT OF LUBRICATING OIL AND ABOUT 10 TO 45 WT. PERCENT OF MIXED METAL SALT OF C1 TO C6 FATTY ACID, C7 TO C30 FATTY ACID AND PHORONIC ACID MATERIAL OF THE FORMULA: 